JPS61256723A - Formation of x-ray mask - Google Patents

Abstract

PURPOSE:To obtain a mask of submicron level when forming an X-ray mask of a predetermined shape on an Si substrate by laminating a Ta film, an Si resin layer and an electron beam resist layer on the substrate, among which only the resist layer has a predetermined mask shape, and removing the exposed parts of the laminated films by etching. CONSTITUTION:When the mask 5 of a predetermined shape whose uppermost layer consists of an Si resin layer is formed on an Si substrate 1, a Ta film 2, and an Si resin layer 3 such as of metyl silsesquioxane are laminated firstly over the entire surface of the substrate 1. The substrate is put in a parallel flat type dry etching device to modify the surface of the layer 3. Next, the surface is coated with an electron beam resist layer 4 such as of chlorometylated polystylene and the layer 4 is made into a pattern 5 of a predetermined shape by exposure and development. By using this as a mask, the underlying Si layer 3 and Ta film 2 are removed by etching utilizing plasma or the like, so that the surface of the substrate 1 is exposed among the patterns 5. Thus, the pattern 5 of submicron level can be obtained and the reduction of stress of the Ta film 2 becomes possible.

Description

[Detailed Description of the Invention] [Summary] Tantalum (Ta) used as a material for X-ray masks
*Heavy metals such as gold (Au) reflect electron beams when irradiated with them, but these scattered electrons make it difficult to form fine patterns.

The present invention is a method for forming an X-ray mask that can form a submicron pattern by providing a scattered electron absorbing layer made of a silicone resin layer on a heavy metal film.

[Industrial application field]

The present invention relates to a method for forming an X-ray mask pattern.

2. Description of the Related Art In order to meet the demand for information processing technology that processes large amounts of information at high speed, semiconductor devices, which are the main components of information processing devices, are becoming increasingly integrated.

In other words, although the maximum area of a semiconductor chip remains almost the same, the number of components increases, and from RC to LSI, LSI
Higher integration is being achieved from SI to VLSI.

Such integration is achieved by miniaturizing unit elements, and this miniaturization is largely due to advances in photolithography as well as semiconductor layer formation technology and thin film formation technology.

Photo-etching technology involves coating a photosensitive resist on the substrate to be processed and selectively exposing it by irradiating it with light or ionizing radiation.The exposed and unexposed areas are exposed to a developer. A resist pattern is created by taking advantage of the difference in solubility caused by the difference in solubility.

Then, using this resist pattern as a mask, dry etching or wet etching is performed to selectively etch the substrate to be processed, thereby forming a fine pattern.

Now, as semiconductor integrated circuits become more highly integrated, the pattern width increases to 1.
Although it is necessary to form a so-called submicron pattern with a size of less than μm, it is impossible to form such a fine pattern using conventional pattern forming methods that use ultraviolet light as a light source. A method is used to draw fine patterns, selectively expose them to light, and selectively etch them.

The photo-etching technology that uses X-rays uses soft X-rays with a wavelength of 5 to 15 people instead of light, and exposes the resist through a mask. It can be exposed to light, the exposure time is short, there is no scattering of electrons unlike with electron beams, sharp fine patterns can be created, and there is no need to use a special vacuum.

However, it requires the use of an X-ray mask.

In other words, a mask made of heavy metal with fine patterns cut out is required.

[Conventional technology]

The material for the X-ray mask must be a material that does not transmit X-rays, so heavy metals are selected, and Ta, Ta,
Au etc. are used.

However, even if this metal is used as a substrate to be processed, an electron beam resist sensitive to electron beams is coated on it, and a fine pattern is drawn by scanning with an electron beam, heavy metals cannot be conventionally used as substrates to be processed. The reflection coefficient of electrons is larger than that of silicon (Si) and aluminum (AI), which are commonly used, and electrons are reflected and scattered, making it impossible to form fine patterns.

For this purpose, a two-layer resist process has been proposed.

That is, a resin layer made of an organic substance is provided on a substrate to be processed, and a resist layer that is highly sensitive to electron beams is provided on this resin layer.

When an electron beam is scanned to draw a fine pattern, the electrons reach the substrate to be processed and are reflected, but since they are absorbed by the resin layer, few of them reach the resist layer on top, so the resist mask for the fine pattern is formed.

However, for this purpose, the thickness of the resin layer must be 2.5 to 3.0 μm.
If the resin layer is thus thick, there is a problem that when dry etching is performed using the resist layer as a mask, the resin layer is undercut and pattern accuracy is reduced.

In addition, in order to reduce the energy of scattered electrons, it is considered that a silicon dioxide (5iO2) layer is formed as an electron absorption layer on the substrate to be processed made of heavy metal, and a resist layer that is sensitive to electron beams is provided on top of this. has been done.

However, metals such as Ta, which are often used as substrates, are very easily broken, and if sio z N is formed thereon by sputtering, stress will be generated on the substrate to be processed and cracks will easily occur. There is a problem in that it requires strict control of internal stress.

[Problem that the invention seeks to solve]

As mentioned above, it is necessary to use heavy metals as X-ray mask materials, but when scanning with an electron beam to draw a submicron pattern on the upper layer of electron beam resist, the electron beam resist is exposed to light by the reflected electrons from the heavy metal. However, there is a problem in that fine patterns cannot be obtained.

[Failure to solve the problem]

The above problem can be solved by providing a scattered electron absorbing layer made of a silicone resin layer on a heavy metal film, then forming an electron beam resist layer on the layer, drawing an electron beam on this layer, and then developing it to form a resist pattern. This problem can be solved by a method for forming an X-ray mask, which is characterized in that a silicone resin layer and a heavy metal film are sequentially selectively etched using the resist pattern as a mask to obtain a mask made of heavy metal.

[Effect]

The present invention realizes a submicron mask made of the mask metal to be processed by providing a silicone resin layer between the mask metal to be processed and the electron beam resist layer and absorbing scattered electrons.

Furthermore, by providing a non-photosensitive resin layer on this silicone resin layer and providing an electron beam resist layer on top of this, scattered electrons are completely prevented from reaching the electron beam resist layer. .

That is, the present invention utilizes the properties of silicone resin, which has an excellent ability to absorb electrons, is easy to form a layer, and hardly generates stress on the mask metal to be processed.

〔Example〕

The silicone resin layer used in the present invention is shown in FIGS.
) is formed using a silicone resin as shown in .

Namely, methylsilsesquioxane (-ship name polyladder oxysiloxane), methylsiloxane.

These include phenylsiloxane and methylphenylsilsesquioxane.

Hereafter, using Ta as the mask metal to be processed, 0.21J
An example of forming a submicron mask having a width of m will be described.

Example 1: (1 structure) A Ta film 2 is deposited on a Si substrate 1 at a thickness of approximately 0°8 by sputtering.
A silicone resin layer 3 made of methylsilsesquioxane (Japan Synthetic Rubber Co., Ltd., trade name PLO3-M) was formed thereon to a thickness of 0.4 μm. [Figure 2 (A)] The method was to apply a cyclohegisanone solution of PLOS-M by a spin cord method, and then heat it at 200° C. for 1 hour to cure it.

Next, the sample was placed in a parallel plate dry etching device, oxygen (02) gas was introduced, and the gas pressure was 8 Pa (
Pascal), applied power density 0.33 W/cm2°, processing time 1 minute, and plasma treatment was performed to form silicone resin layer 3.
The surface was modified to restore wettability.

Chloromethylated polystyrene (Toyo Soda Co., Ltd.: trade name CMS-EX) is coated on top of this silicone resin layer 3 using a spin code method.
) and prebaked at 100° C. for 30 minutes in a nitrogen (N2) stream to form an electron beam resist layer 4 with a thickness of 0.6 μm. [Figure 2 (B)] Next, after drawing a fine pattern by scanning the electron beam resist layer 4 with an electron beam at an acceleration voltage of 20 KV, the sample was immersed in acetone for 60 seconds to develop it. Furthermore, rinsing treatment was performed by immersing it in isopropanol for 30 seconds.

As a result, a resist pattern 5 of 0.5 μm line and space could be formed.

Note that the pattern drawing sensitivity was 20 μC/CnI2. [Figure 2 (C)] Next, Freon (C) is applied using the resist pattern 5 as a mask.
Fa ) gas was used, the gas pressure was 8 Pa, and the applied power density was 0.
33W/cm2. The pattern was transferred to the silicone resin layer 3 by plasma etching with a processing time of 4 minutes. [Figure 2 (D)] Next, chlorine (C1,z) gas and carbon tetrachloride (C(:la
) using a mixed gas with a concentration ratio of 1:1 and a gas pressure of 8 Pa.
.

Applied power density 0.33W/cm2. The pattern was transferred to the Ta film 2 by plasma etching with a processing time of 3 minutes. [FIG. 2(E)] As a result of the above, a 0.5 μm line-and-space Zabumicron Ta pattern could be formed.

Example 2: (Three-layer structure) A Ta film 2 with a thickness of about 0°8 μm was formed on the Si substrate 1 by sputtering, and methyl silsesquioxane (Japan Synthetic Rubber Co., Ltd.: trade name) was deposited on top of this. A silicone resin layer 3 made of PLO3-M) was formed to a thickness of 0.4 μm.

The method was to apply a cyclohexanone solution of PLO3-M using a spin code method, and then heat it at 200° C. for 1 hour to cure it.

Next, the sample was placed in a parallel plate dry etching device, oxygen (02) gas was introduced, and plasma treatment was performed under the conditions of a gas pressure of 8 Pa (pascal), an applied power density of 0.33 W/cm2°, and a treatment time of 1 minute. The surface of the silicone resin layer 3 was modified to restore wettability.

Poly p-hydroxystyrene (Maruzen Oil Co., Ltd.: trade name POP-6829) and 0-talesol novolac resin (Sumitomo Chemical Co., Ltd.: trade name Sumiepoxy E) are placed on this silicone resin layer 3.
A non-photosensitive resin layer 6 consisting of SCN-195-6) was formed to have a thickness of 0.5 μm.

In this formation method, a cyclohexane solution mixed at a weight ratio of 2:1 is applied onto the silicone resin layer 3 by a spin code method, and then heated at 200° C. for 1 hour to harden it. [Figure 3 (A)] Next, silylated polymethylsilsesquioxane (average weight molecule 1t33000.
The electron beam resist layer 7 having a dispersion degree of 1.36) has a dispersity of 0.2
Formed to the thickness of the μ river.

In this formation method, a 4-methyl-2-pentanone solution of silylated polymethylsilsesquioxane was applied by a spin cord method, and prebaked at 80° C. for 20 minutes in a N2 stream.

As a result, a resist layer having a two-layer structure consisting of the non-photosensitive resin layer 6 and the electron beam resist layer 7 was formed. [Figure 3 (
B)] As a pattern forming method, after drawing a fine pattern on the electron beam resist layer 7 by scanning an electron beam in the same manner as in Example 1, a mixed solution (mixture) of 4-methyl-2-pentanone and isopropanol was applied. ratio 2:8) to 3
After being immersed for 0 seconds and developed, it was immersed in isopropanol for 30 seconds and rinsed. [Figure 3 (C)] Next, the sample was placed in a parallel plate type dry etching device,
0□ Gas was introduced, the gas pressure was 2 Pa, and the applied power density was 0.
22W/cm2. The resist pattern 8 was transferred to the non-photosensitive resin layer 6 by plasma etching for a processing time of 5 minutes, thereby forming a two-layer resist pattern with 0.3 μm lines and spaces. [Figure 3 (D)] Next, the etching gas is CCI 4 and CF.
, the gas pressure was 8 Pa, and the applied power density was 0.33 W/cm2. By performing plasma etching for a processing time of 10 minutes, it was possible to form a 0.3 μm line-and-space Ta pattern by etching the silicone resin layer 3 and the Ta film 2 together. [Figure 3 (E)] [Effects of the Invention] As described above, by implementing the present invention, it is possible to form submicron patterns, and stress is not generated in the Ta substrate during the formation of the silicon resin layer. Since there is no X-ray pattern, it is possible to create an X-ray pattern with high yield.

[Brief explanation of the drawing]

Figure 1 shows silicone resin that can be applied to the present invention, Figure 2 (
A) to (E) are the manufacturing process of a two-layer structure mask, and FIGS. 3A to 3E are the manufacturing process of a three-layer structure mask. In the figure, 1 is an St substrate, 2 is a Ta film, 3 is a silicone resin layer, 4.7 is an electron beam resist layer, 5.8 is a resist pattern, and 6 is a non-photosensitive resin layer. Kite 1 stop length 12 noshiru winter long 1 efe; lshienoki A? Gimei ni saiyo fu°machi negative ρ Relicon's finger part 1 Figure % 2 Figure 3

Claims (2)

[Claims] (1) After providing a scattered electron absorption layer consisting of a silicone resin layer (3) on the heavy metal film, an electron beam resist layer (
4) is drawn with an electron beam and then developed to form a resist pattern (5), and using the resist pattern (5) as a mask, the silicone resin layer (3) and the heavy metal film are sequentially selectively etched. A method for forming an X-ray mask, the method comprising obtaining a mask made of heavy metal. (2) After providing a scattered electron absorption layer consisting of a silicone resin layer (3) on the heavy metal film, a non-photosensitive resin layer (6
) and an electron beam resist layer (7) are formed, which are subjected to electron beam drawing and later developed to form a resist pattern (8). Using the resist pattern (8) as a mask, a non-photosensitive resin layer ( 6) A method for forming an X-ray mask, which comprises sequentially selectively etching the silicone resin layer (3) and the heavy metal film to obtain a mask made of heavy metal.